atmel-mci: fix initialization of dma slave data

The conversion of atmel-mci to dma_request_channel missed the
initialization of the channel dma_slave information.  The filter_fn passed
to dma_request_channel is responsible for initializing the channel's
private data.  This implementation has the additional benefit of enabling
a generic client-channel data passing mechanism.

Reviewed-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Acked-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index 3e68469..f041384 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -121,6 +121,7 @@
  * @local: per-cpu pointer to a struct dma_chan_percpu
  * @client-count: how many clients are using this channel
  * @table_count: number of appearances in the mem-to-mem allocation table
+ * @private: private data for certain client-channel associations
  */
 struct dma_chan {
 	struct dma_device *device;
@@ -134,6 +135,7 @@
 	struct dma_chan_percpu *local;
 	int client_count;
 	int table_count;
+	void *private;
 };
 
 /**